For the purpose of this Chapter, the following definitions shall apply:

   "Appurtenant facilities" means any building, structure or other property which is incidental to, and customarily found in connection with, major facilities of public utilities and are operated and maintained for the benefit or convenience of the occupants, employees, customers or visitors of such major facilities.

   "Major facilities of a public utility" means transmission lines, power plants, substations, pipelines, and storage areas of utilities as herein separately defined.

   "Nonconforming use" means a use in existence on the effective date of this designation (April 7, 1977) which is a "major facility of a public utility." When such a nonconforming use is discontinued for six months or more, or is damaged or destroyed to the extent of fifty (50) percent of the appraised value, then the protection afforded the nonconforming use shall cease and a permit shall be required to recommence or replace the use.

   "Pipelines" mean any pipeline and appurtenant facilities thereto, designed for, or capable of, transporting natural gas, manufactured gas, or other petroleum derivatives of ten (10) inches or more in diameter which creates a hoop stress of twenty (20) percent or more at their specified minimum yield strength.

   "Power plant" means any of the following:

        1.  Any fossil fuel, biofuel, or similar electrical energy generating facility with a generating capacity of one hundred (100) megawatts or more, and any appurtenant facilities thereto, or any addition or series of additions thereto increasing the existing design capacity of the facility by one hundred (100) megawatts or more.

        2.  Any solar or wind electrical energy generating facility with a generating capacity in excess of two (2) megawatts, and any appurtenant facilities thereto, or any addition or series of additions thereto increasing the existing design capacity of the facility in excess of two (2) megawatts.

        3.  Any nuclear or hydropower electrical generating facility.

   "Public utilities" mean those utilities as defined by 39-4-101, C.R.S. 1973.

   "Storage area" means any facility, including appurtenant facilities, designed to store eighty million (80,000,000) cubic feet or more of natural or manufactured gas, or thirty-five thousand (35,000) barrels or more of petroleum derivatives, or any expansion or series of expansions of an existing storage facility to accommodate eighty million (80,000,000) cubic feet or more of natural or manufactured gas, or thirty-five thousand (35,000) barrels or more of petroleum derivatives.

   "Substation" means any facility designed to provide switching, voltage transmission, or voltage control required for the transmission of electricity at one hundred fifteen (115) kilovolts or more, but does not have as a primary purpose the transformation of voltage to fifty (50) kilovolts or less for distribution purposes.

   "Transmission lines" mean any electric transmission line and appurtenant facilities, which transmit electricity at one hundred fifteen (115) kilovolts or more.